Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 2 — Questions and Answers
Question 1: Which of the following best describes the function of the smooth endoplasmic reticulum (SER)?
- Protein synthesis and folding
- Lipid synthesis and detoxification (Correct answer)
- Packaging proteins into vesicles
- DNA replication and transcription
Correct answer: Lipid synthesis and detoxification
The SER lacks ribosomes and is involved in lipid and steroid synthesis, detoxification of drugs, and calcium storage.
Question 2: During the Calvin cycle (light-independent reactions), CO₂ is first fixed to produce:
- Glyceraldehyde-3-phosphate (G3P)
- Ribulose-1,5-bisphosphate (RuBP)
- Two molecules of 3-phosphoglycerate (3-PGA) (Correct answer)
- One molecule of oxaloacetate
Correct answer: Two molecules of 3-phosphoglycerate (3-PGA)
RuBisCO catalyzes the carboxylation of RuBP with CO₂ to form an unstable 6-carbon compound that immediately splits into two molecules of 3-PGA.
Question 3: Which type of transport requires no energy input and moves substances from high to low concentration?
- Active transport
- Endocytosis
- Facilitated diffusion (Correct answer)
- Pinocytosis
Correct answer: Facilitated diffusion
Facilitated diffusion uses protein channels or carriers to move substances down their concentration gradient without ATP expenditure.
Question 4: A competitive inhibitor of an enzyme reduces reaction rate by:
- Permanently denaturing the enzyme's tertiary structure
- Binding to the allosteric site and changing enzyme shape
- Occupying the active site and blocking substrate binding (Correct answer)
- Increasing the activation energy of the reaction
Correct answer: Occupying the active site and blocking substrate binding
Competitive inhibitors have a structure similar to the substrate and reversibly bind to the active site, competing directly with the substrate.
Question 5: Which stage of aerobic respiration yields the greatest number of ATP molecules?
- Glycolysis
- Pyruvate oxidation
- Krebs cycle
- Oxidative phosphorylation (electron transport chain) (Correct answer)
Correct answer: Oxidative phosphorylation (electron transport chain)
Oxidative phosphorylation via the electron transport chain produces approximately 28–32 ATP per glucose, far exceeding the other stages.
Question 6: In plant cells, the large central vacuole primarily functions to:
- Carry out photosynthesis
- Synthesize proteins for secretion
- Maintain turgor pressure and store waste products (Correct answer)
- Produce ATP through cellular respiration
Correct answer: Maintain turgor pressure and store waste products
The central vacuole stores water, ions, and waste products while creating turgor pressure that supports the plant cell and drives cell expansion.
Question 7: During meiosis, genetic diversity is increased by which two primary mechanisms?
- Mitotic division and chromosome replication
- Crossing over (recombination) and independent assortment (Correct answer)
- DNA mutation and gene amplification
- Centromere splitting and cytoplasmic division
Correct answer: Crossing over (recombination) and independent assortment
Crossing over during prophase I exchanges segments between homologous chromosomes, while independent assortment randomly distributes homologs to gametes.
Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 2
Which of the following best describes the function of the smooth endoplasmic reticulum (SER)?